Fibre channel elastic FIFO delay controller and loop delay method having a FIFO threshold transmission word adjuster for controlling data transmission rate

Abstract

In a circuit coupled to a port of a network having a loop architecture, a read/write pointer controller provides a read and a write pointer to track transmission words stored in a FIFO array. The read/write pointer controller also provides a FIFO level indicator to track the total number of transmission words in the FIFO array. A dynamic threshold controller tracks transmission word insertions and deletions in the FIFO array for a predetermined period of time and provides a threshold level adjustment signal based on the tracked transmission word insertions and deletions and a transmission word threshold level. A FIFO level adjuster provides transmission word insert and delete commands and adjusts the threshold level of the FIFO array in response to the threshold level adjustment signal.

1. A circuit coupled to a port of a storage network having a loop architecture, said circuit comprising:
 a read/write pointer controller configured to provide a FIFO level indicator to track a total number of transmission words stored in a FIFO array; 
 a dynamic threshold controller, responsive to said FIFO level indicator and to transmission word insert and delete commands, configured to track transmission word insertions and deletions in said FIFO array for a predetermined time period and provide a transmission word threshold level adjustment signal based on said tracked transmission word insertions and deletions for said predetermined time period and a transmission word threshold level; and 
 a FIFO threshold adjuster, responsive to the FIFO level indicator and the transmission word threshold level adjustment signal, to provide the transmission word insert and delete commands based on both a data transmission rate difference between received input data and transmitted output data and the FIFO level indicator and to adjust the transmission word threshold level based on the transmission word threshold level adjustment signal, 
 wherein the transmission words are maintained to account for the data transmission rate difference between received input data and transmitted output data. 
 
   
   
     2. The circuit of  claim 1 , wherein said FIFO threshold adjuster adjusts the transmission word threshold level using the transmission word insert and delete commands. 
   
   
     3. The circuit of  claim 2 , wherein the transmission word threshold level has an initial value of three transmission words. 
   
   
     4. The circuit of  claim 2 , wherein said dynamic threshold controller provides the transmission word threshold level adjustment signal having a threshold value, the threshold value being lower than said transmission word threshold level if only the transmission word deletions occur during the predetermined time period, and the threshold value being equal to or higher than the transmission word threshold level otherwise. 
   
   
     5. The circuit of  claim 4 , wherein responsive to the transmission word threshold level adjustment signal, said FIFO threshold adjuster lowers the transmission word threshold level to the threshold value. 
   
   
     6. The circuit of  claim 5 , wherein the FIFO array has a minimum threshold level of one transmission word. 
   
   
     7. The circuit of  claim 4 , wherein responsive to the transmission word threshold level adjustment signal, said FIFO threshold adjuster maintains the transmission word threshold level if the threshold value is equal to the transmission word threshold level or raises the threshold level if the threshold value is greater than the transmission word threshold level. 
   
   
     8. The circuit of  claim 7 , wherein the FIFO array has a maximum threshold level of six transmission words. 
   
   
     9. The circuit of  claim 1 , wherein said read/write pointer controller further provides a read and a write pointer to track the transmission words stored in the FIFO array. 
   
   
     10. A circuit coupled to a port of a storage network having a loop architecture, said circuit comprising:
 a read/write pointer controller means to provide a FIFO level indicator means to track a total number of transmission words stored in a FIFO array; 
 a dynamic threshold controller means, responsive to the FIFO level indicator means and to transmission word insert and delete commands, to track transmission word insertions and deletions in the FIFO array for a predetermined time period and provide a transmission word threshold level adjustment signal based on said tracked transmission word insertions and deletions for the predetermined time period and a transmission word threshold level; and 
 a FIFO threshold adjusting means, responsive to the FIFO level indicator and the transmission word threshold level adjustment signal, to provide the transmission word insert and delete commands based on both a data transmission rate difference between received input data and transmitted output data and the FIFO level indicator means and to adjust the transmission word threshold level based on the transmission word threshold level adjustment signal, 
 wherein the transmission words are maintained to account for the data transmission rate difference between received input data and transmitted output data. 
 
   
   
     11. The circuit of  claim 10 , wherein said FIFO threshold adjusting means adjusts the transmission word threshold level using the transmission word insert and delete commands. 
   
   
     12. The circuit of  claim 11 , wherein the transmission word threshold level has an initial value of three transmission words. 
   
   
     13. The circuit of  claim 11 , wherein said dynamic threshold controller means provides the transmission word threshold level adjustment signal having a threshold value, the threshold value being lower than the transmission word threshold level if only the transmission word deletions occur during the predetermined time period, and the threshold value being equal to or higher than the transmission word threshold level otherwise. 
   
   
     14. The circuit of  claim 13 , wherein responsive to the transmission word threshold level adjustment signal, said FIFO threshold adjusting means lowers the transmission word threshold level to the threshold value, and wherein the FIFO array has a minimum threshold level of one transmission word. 
   
   
     15. The circuit of  claim 13 , wherein responsive to the transmission word threshold level adjustment signal, said FIFO threshold adjusting means maintains the transmission word threshold level if the threshold value is equal to the transmission word threshold level or raises the threshold level if the threshold value is greater than the transmission word threshold level, and wherein the FIFO array has a maximum threshold level of six transmission words. 
   
   
     16. The circuit of  claim 10 , wherein the read/write pointer controller means further provides a read and a write pointer to track the transmission words stored in the FIFO array. 
   
   
     17. A method, comprising:
 tracking transmission word insertions and deletions for a predetermined period of time, wherein the transmission word insertions are in response to a slower input data transmission rate relative to an output transmission rate, and wherein the transmission word deletions are in response to a faster input data transmission rate relative to the output transmission rate; 
 responsive to said tracking, if only transmission word deletions are tracked for the predetermined period of time, lowering a transmission word threshold level in a computer readable storage medium; 
 responsive to said tracking, if both transmission word insertions and deletions are tracked for the predetermined period of time, determining whether the transmission word threshold level in the computer readable storage medium has been previously lowered; and 
 responsive to said determining, raising the transmission word threshold level if the transmission word threshold level has been previously lowered, 
 wherein the transmission words are maintained to account for a difference between the input data transmission rate and the output transmission rate. 
 
   
   
     18. The method of  claim 17 , wherein a fill character threshold level has a default level of three fill characters and a minimum level of one fill character, and wherein said lowering and said raising the transmission word threshold level are performed in one transmission word increments. 
   
   
     19. The method of  claim 18 , further comprising, if the transmission word threshold level equals a default transmission word threshold level and both transmission word insertions and deletions are tracked for the predetermined period of time, maintaining the transmission word threshold level at the default transmission word level. 
   
   
     20. A storage network having a loop architecture, the storage network comprising:
 a plurality of ports, each port electrically connected to an upstream port and a downstream port; 
 a plurality of storage devices, each storage device connected to each port of the plurality of ports; and 
 a circuit according to  claim 1  coupled to each port of the plurality of ports, the circuit to adjust data transmission delay in the port based on a data transmission rate difference between data transmitted from the upstream port and data transmitted to the downstream port, 
 wherein the transmission words are maintained to account for the data transmission rate difference between received input data and transmitted output data. 
 
   
   
     21. The network of  claim 20 , wherein said FIFO threshold adjuster adjusts said transmission word threshold level using said transmission word insert and delete commands, said transmission word threshold level having an initial value of three transmission words. 
   
   
     22. The network of  claim 21 , wherein said dynamic threshold controller provides said transmission word threshold level adjustment signal having a threshold value, said threshold value being lower than said transmission word threshold level if only said transmission word deletions occur during said predetermined time period, and said threshold value being equal to or higher than said transmission word threshold level otherwise. 
   
   
     23. The network of  claim 22 , wherein responsive to said transmission word threshold level adjustment signal, said FIFO threshold adjuster lowers said transmission word threshold level to said threshold value, and wherein said FIFO array has a minimum threshold level of one transmission word. 
   
   
     24. The network of  claim 22 , wherein responsive to said transmission word threshold level adjustment signal, said FIFO threshold adjuster maintains said transmission word threshold level if said threshold value is equal to said transmission word threshold level or raises said threshold level if said threshold value is greater than said transmission word threshold level, and wherein said FIFO array has a maximum threshold level of six transmission words. 
   
   
     25. The network of  claim 20 , wherein said read/write pointer controller further provides a read and a write pointer to track the transmission words stored in the FIFO array.